JP3020488B2 - Liquid micro pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid microvalve and a micropump. More specifically, the present invention relates to a micro liquid microsystem useful for a system for monitoring the pH of blood and a liquid chromatography system for separating and analyzing a trace amount of biological substances in biological fluids such as blood, urine, and cerebrospinal fluid. It relates to valves and micropumps.

[0002]

2. Description of the Related Art Liquid chromatographs used for blood pH monitoring systems and chemical analysis have already been developed and put to practical use with various systems and configurations.
However, each of them has a large mechanical part such as a valve and a pump and a detecting part, and has a limitation that a measurement sample is required to be a certain amount or more, and there is a problem that a measurement time is further required.

[0003] In particular, a continuous monitoring system for blood pH,
Separates biological substances in biological fluids such as blood, urine, and cerebrospinal fluid
In a system for analysis, it is essential that a very small amount of a measurement sample can be measured at a high speed. However, the current system cannot satisfy this requirement. In order to solve such problems, ultra-compact integrated gas chromatography in which a pump and a column are formed on a silicon substrate has been proposed. However, there is a problem in accuracy and resolution, such as large pulsation, which causes noise in the detector of the analyzer, and has not been put to practical use.

[0004] When a microvalve or a micropump is formed on a silicon substrate by using micromachining technology, those used for liquid analysis require more advanced manufacturing techniques than those for gas. Furthermore, practical application is difficult. The reasons are as follows. First
In addition, since liquid is more viscous than gas, a liquid valve needs to have a smaller resistance in a flow path and a valve part than a gas valve, and the dimensions of each must be increased. Second, it is necessary to increase the displacement of the valve and the actuator that moves the valve accordingly, and it is not easy to select a valve or an actuator that operates stably under such a large displacement. Third, in the case of a pump, a check valve for preventing backflow is required, and it is extremely difficult to select a material and design a structure for stable operation. Fourth, because the dimensions of the flow path and the valve become large,
It is necessary to use a strong substrate, and it is necessary to develop a joint between the substrates with safe airtightness.
This has not been realized until now.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems and technical problems, and provides a micro valve or micro pump for a liquid formed by using a micro machining technique. It is intended to be. Furthermore, the present invention also provides a system capable of analyzing a very small amount of biological fluid at high speed and with high accuracy.

[0006]

In order to achieve the above object, the present invention provides a silicon substrate having a liquid flow path and a liquid introduction / exit hole, a silicon substrate or a glass substrate having a liquid flow path. A valve of silicon rubber sheet and an actuator for opening and closing this valve are arranged.The actuator pushes the valve against the inlet / outlet hole, closes it, and opens the valve by returning the actuator. A liquid micro valve of normally open type or normally closed type is provided.

[0007] The present invention also provides a liquid micropump provided with a silicon substrate on which a mesa and a diaphragm are formed, a check valve, and an actuator.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a liquid microvalve and a micropump according to the present invention will be described with reference to the drawings. FIG. 1 illustrates the structure of normally closed and normally open microvalves as an example of the present invention. In this example, an actuator (3) including a shape memory alloy coil (1) and a bias spring (2) is provided to realize a displacement of a valve of several hundreds of micrometers.

The structure of this example is composed of a glass substrate (6) having an aluminum plate (4) as a support material and having a flow path (5) formed thereon by etching or sandblasting to increase the strength. The fluid flow is performed by hermetically joining a flow path (7) finely processed by micromachining technology utilizing properties such as crystal axis anisotropy of the silicon substrate and a silicon substrate (9) having a liquid inlet / outlet hole (8). A path is formed, a silicon rubber sheet (10) is adhered, this is used as a valve, an aluminum plate (11) is laminated as a reinforcing plate, and the above-mentioned actuator (3) is provided.

The Pyrex glass substrate (6) and the silicon substrate (9) are bonded to each other by 350
The anodic bonding can be performed by applying a voltage of, for example, 500 V with the Pyrex glass substrate (6) being on the minus side under heating at a temperature of 500C to 500C. FIG. 2 illustrates another example structure. An aluminum plate (17) having a liquid flow path formed by anodically bonding a Pyrex glass substrate (12) (13) and a silicon substrate (14), and using a silicon rubber sheet (15) as a valve; The plate (16) is used as a support material. This example is characterized in that the actuator (18) is a piezo bimorph type. This provides deformation using the piezoelectric effect, and has the characteristics that the response time is about 1/100 and the power consumption is small as compared with the shape memory alloy actuator.

In the case of the example shown in FIG. 2, a normally open structure is shown. However, with the same structure, the piezo bimorph is fixed while pressing the silicon rubber sheet, and the structure is reversed by applying a voltage. By moving in the direction, a normally closed type can be easily achieved. FIG. 3 is a characteristic diagram showing a flow control state obtained by the example of the present invention. FIG. 3A shows a normally open type, and FIG. 3B shows a normally closed type. This indicates that a very small flow rate control of several ml / min is possible.

FIGS. 4 and 5 are views showing an application example of the liquid microvalve of the present invention. FIG. 4 schematically shows the blood pH monitor microsystem, and FIG. 5 shows the internal structure thereof. In this system, as shown in FIG. 4, a Ringer's solution (20) and a calibration solution (21) are sent, and blood flows through an indwelling needle (22). The waste liquid is discharged through a suction pump (23).

As shown in FIG. 5, this system has a liquid microvalve (24) (25) and an ISFET (26) as a pH sensor integrated on a silicon substrate, and a comparative electrode (27). It is also provided with a device for intermittently collecting blood outside the body and performing pH analysis. The microvalve (24) is of a normally open type and the microvalve (25) is of a normally closed type. Usually, it is attached to the indwelling needle (22) part of the device for supplying the infusion liquid to the body, so that the infusion liquid is supplied into the body and blood is collected through the same needle only at the time of measurement to perform the analysis. further,
The feature of this structure is that it has a function of automatically calibrating the sensor immediately before the measurement using the calibration liquid (21), and therefore one normally open micro valve (24) And two normally closed microvalves (25), and the flow of blood, Ringer's solution (20) and calibration solution (21) from the indwelling needle (22) can be freely changed.

FIG. 6 shows the operating characteristics of the pH monitor microsystem as an application example. The time required for one cycle of measurement is greatly reduced to about 20 seconds. FIG. 7 shows an example of a liquid micropump. This includes a glass substrate (33) having a liquid outlet hole (30) and a concave portion (32) on the joint surface with the silicon substrate (31), a liquid inlet hole (34) and a liquid outlet hole. A silicon substrate (31) having (35) and a silicon substrate (38) having a mesa (36) processed by micromachining technology and a diaphragm (37) are laminated and bonded so as to be completely airtight. It consists of a structure.
A check valve (39) for preventing backflow is provided on the substrate surface corresponding to the liquid outlet side of the silicon substrate (31) of the intermediate layer having the liquid inlet hole (34) and the outlet hole (35). Characteristically, the diaphragm (37) is moved by an actuator (40) disposed below the diaphragm (37), thereby opening and closing the check valve (39).

A check valve (41) is also provided in the liquid inlet hole (34). The micromachining technology and anodic bonding technology used are the same as described above. Furthermore, low-melting glass is added to one of the substrates as a bond between silicon substrates.
After coating by the F sputtering method, a method of anodic bonding is also applicable. In this embodiment, a laminated piezo actuator can be used, but it goes without saying that any form of ultra-small actuator capable of obtaining a large displacement is applicable.

FIG. 8 illustrates the structure of the microminiature check valve used in this embodiment. It has four beams (4
A disc-shaped polycrystalline silicon film (43) supported by 2) is used, and a through hole formed in a silicon substrate is opened and closed by a pressure difference between both ends of a valve. The pressure loss and the pressure-flow rate characteristics of the valve portion vary depending on the size of the beam (42) and the dimensional ratio between the disk portion and the through-hole.
If 0 × 50 μm 2, the radius r1 of the disc valve is 200 μm, and the width W and length L of the beam are 200 μm and 300 μm, respectively, a flow rate of 150 nl / min can be extruded at a pressure of 2 kg / cm 2.

[0017] The micro liquid pump according to the present invention is as follows.
One application example is an ultra-high-performance liquid chromatography system.

[0018]

As described above, according to the present invention, there is provided a liquid microvalve or liquid micropump useful for a microminiature liquid analysis system expected to have various applications. Since the pulse volume can be reduced, and the integration is possible, there is no problem of the invalid volume of the piping. It can be integrated with a flow meter or pressure gauge such as a differential pressure pump, or can be integrated with another pump to eliminate the pulse rate as a dual pump.
High-speed, high-precision measurement of a very small amount of liquid sample becomes possible.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a liquid microvalve of the present invention.

FIG. 2 is a sectional view showing another example of the liquid microvalve of the present invention.

FIG. 3 is a correlation diagram showing a voltage-flow rate characteristic of the liquid microvalve of the present invention, wherein (a) shows a normally open type and (b) shows a normally closed type. .

FIG. 4 shows blood p using the liquid microvalve of the present invention.
It is the perspective view shown about the H monitor microsystem.

FIG. 5 is a sectional view of the blood pH monitor microsystem shown in FIG. 4;

6 is an operation characteristic diagram of the blood pH monitor micro system shown in FIG.

FIG. 7 is a sectional view showing an example of a liquid micropump according to the present invention.

FIG. 8 is a plan view showing an example of a check valve used in the liquid micropump shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shape memory alloy coil 2 Bias spring 3 Actuator 4 Aluminum plate 5 Flow path 6 Glass substrate 7 Flow path 8 Inlet / outlet hole 9 Silicon substrate 10 Silicon rubber sheet 11 Aluminum plate 12, 13 Glass substrate 14 Silicon substrate 15 Silicon rubber sheet 16, 17 Aluminum plate 18 Actuator 24, 25 Micro valve 26 ISFET 30 Outlet 31 Silicon substrate 32 Concave 33 Glass substrate 34 Inlet 35 Outlet 36 Mesa 37 Diaphragm 38 Silicon substrate 39 Check valve 40 Actuator 41 Check valve 42 Beam 43 polycrystalline silicon film

Claims (3)

(57) [Claims] 1. A glass substrate having a concave portion on a bonding surface together with a liquid outlet hole, an intermediate silicon substrate having a liquid inlet / outlet hole, and a silicon substrate having a mesa and a diaphragm are laminated and completely air-tightly bonded. It has a check valve on the substrate surface corresponding to the liquid outlet side of the intermediate layer silicon substrate, and an actuator for moving the diaphragm and opening and closing the check valve is arranged at the lower part of the diaphragm. Liquid micro pump. 2. The liquid micropump according to claim 1, wherein the check valve is formed of disk-shaped polysilicon supported by beams. 3. The liquid micropump according to claim 1, wherein the glass substrate and the silicon substrate or the silicon substrates are hermetically bonded by anodic bonding.